This is an unusual resource (so far) in that it cannot be created in one
call, and instead must be created and the modified to set some of the
parameters.
We use the pollIndefinitelyWhileNeeded function which will continue to
poll Azure RM operation monitoring endpoints until an error is reported
or the operation meets one of the given status codes. The function was
originally part of this feature but was separated out in order to
unblock other work.
Currently there is no support for the "custom_domain" section of the
storage account API. This was originally present and was later taken out
of the scope of the storage account resource in order that the following
workflow can be used:
1. Create storage account
2. Create DNS CNAME entry once the account name is known
3. Create custom domain mapping
